The present invention relates to coolant delivery systems for machine tools, and more particularly relates to a novel and improved method and apparatus for automatically positioning a coolant nozzle for the delivery of coolant to the desired location on each of a plurality of different sized cutting tools, specifically to such delivery systems that allow automated control of coolant to a desired location in a machine tool.
In a computerized numerically controlled (CNC) machine tool, the various machining operations to produce a specific part are typically preprogrammed by an operator. The CNC machine tool performs operations, such as, drilling, tapping, and milling, automatically and without the intervention of the operator. In order to perform these operations, the CNC machine tool automatically changes cutting tools, from a drill, to a tap, to an end mill, for instance. During the cutting operations, it is desirable to direct the flow of a cooling fluid, or coolant, at or near the cutting interface. The coolant offers numerous benefits: (1) the coolant prevents the workpiece and tool from overheating, thus reducing scrap and tool costs; (2) the coolant provides a means of lubrication for the cutting tools; (3) the coolant minimizes thermal growth of the workpiece and the cutting tool that would otherwise reduce dimensional accuracy of the workpiece; and (4) the coolant carries away the material removed from the workpiece. When working with a metal workpiece, these chips of material become hardened in the cutting process. If these chips are not carried away, the cutting tool cuts these chips multiple times. Tool life decreases as a result.
When the machine tool changes cutting tools, the optimal position for the coolant stream changes. For example, the optimal coolant stream position for a long drill could be ten inches lower than the optimal coolant stream position for a short tap. Without an automated coolant delivery system, the operator must intervene when a tool is changed to optimize the coolant stream direction. The operator's intervention, to some extent, defeats the efficiency offered by the tool-changing capability of the CNC machine tool.
One prior art automated coolant system requires a motor to automatically position a coolant nozzle. The motorized coolant delivery system brings with it several disadvantages:
a) The cost of the motor increases the cost of the coolant delivery system substantially. The motor is a precise mechanism; cost reduction through high volume production is limited. The type of motor appropriate for this application requires additional electronic control hardware, which also drives the cost higher. Beyond the cost of the electronic control hardware, there is a cost associated with housing the additional electronic control hardware in a suitable environment. Also with motors, come electrical cables. Cable protection components, such as, shrouds and cable tracks are required to protect the cables from the environment surrounding the coolant delivery system. While some of the cable protection components can be shared with those provided for other electronic devices, often these protection components are already overcrowded. In addition, the distance from the electronic control hardware to the motor is often substantial. The cost of the cable, as well as the cost of labor required to install the cable, is significant.
b) Many machine tools have been installed in the field without an automated coolant delivery system. These machines need an easily retrofitted solution. Field installations exacerbate the problem of finding a place to install additional electronic control hardware and route associated electrical cables. Some of the electronic components in a machine tool are very expensive. The potential for damaging these components while installing a motorized coolant delivery system is significant. For this reason, highly skilled service technicians are required. Not only is more time required to install the additional electronic control hardware in the field, the time is more costly because the labor rates for skilled service technicians are quite high.
c) To realize the cost benefits of high volume manufacturing, a solution that works with many different models of machine tools with minimal customization, is desirable. The motorized coolant delivery system requires numerous variations to address the many various electrical control interfaces. This requirement defeats standardization efforts.
d) Software modification is required to implement the motorized coolant delivery system. Besides adding to the cost of implementation, this requirement also defeats standardization efforts.
e) Some of the manufacturers of the prior art motorized coolant delivery system have attempted to minimize cost by using a motor control system with coarse resolution. The coarse resolution results in non-optimal coolant stream settings and the operator is forced to choose a setting that is too high or too low.
As employed herein, the term “cutting tools” is intended to refer to any type of tool employed in the machining center or machine tool to carry out drilling, machining, shaping or grinding operations. Also, the term “coolant” is intended to refer to both liquid and gaseous cooling fluids.